Fix race condition when connecting to fs process

Fixes a regression introduced by 2a73db7e34b: We only tried to
connect to the port 3 times immediately after the fs process was
started, which might be too short.

Instead, expicitly try to connect for 30 seconds, and only give up
then.

Task-number: QTIFW-316
Change-Id: I8a1ba59ff680f4ef536f13230215f2289ab3b0ed
Reviewed-by: Niels Weber <niels.weber@digia.com>